June 2,1923 
Orange Trees in Sand and Soil Cultures 
805 
fertilizers tended to reduce the amount of mottling. Although the 
authors have grown 23 orange trees in sand cultures and 5 in soil receiving 
various concentrations of an inorganic nutrient solution, no typical 
mottle-leaf has been found as yet on any of the trees. 
A word of caution is here necessary as regards the choice of orange 
trees for sand cultures. It seems best to use trees which are free from 
mottle-leaf, although trees which previously bore mottled leaves may 
present no difficulties after their behavior is once known. When mottled 
trees have been used in sand cultures receiving Hoaglands solution, and 
the leaves, shoots, rootlets, etc., removed as before stated, the first cycle 
of growth may bear a few mottled leaves most of which may recover, but 
the subsequent cycles have thus far been free from any evidence of 
mottling. 
In order to observe the effect of the sand on the Ph of the solution, 
some of the nutrient solution was placed in liter Erlenmeyer flasks closed 
with rubber stoppers. Sand was added to one flask, shaken, and allowed 
to stand from December 29, 1920, to January 24, 1921. l^he Ph of the 
nutrient without sand had not changed, while that in contact with sand 
had increased from 5.2 to 5.9. Other culture solutions treated in this 
manner gave similar results. Shive (9) has reported that the reaction 
of his nutrient solution was not markedly altered by contact with un¬ 
washed sand. He finds that sand has an initial adsorptive effect but this 
is soon satisfied in sand cultures where the nutrient solution is renewed 
frequently. The increase in the Ph of the solution in contact with the 
sand was probably due to chemical reactions and not to adsorption. 
The adsorptive property of unwashed sand probably was due to the 
very finely divided colloidal or semicolloidal material which was removed 
from the sand in the process of washing. The Ph values of percolates 
from the cans were determined from time to time to learn whether 
material changes ensued after prolonged contact with the sand and tree 
roots. The results of several determinations on percolates from cans 
I and 2 are given in Table I. The first two determinations showed the 
increase when a nutrient solution having an initial Ph of 5.2 was allowed 
to percolate through the sand of one of the cans. The other determina¬ 
tions show the changes in Ph when distilled water was allowed to per¬ 
colate through the sand. These determinations are more variable, owing 
in part to the fact that the distilled water washed out varying quantities 
of the residual nutrient solution. In eveiy^ case the Ph of the percolate 
tends to move in the direction of neutrality. 
Table I.— Ph values of nutrient solution and percolate from trees grown in sand cultures 
Date. 
Application. 
Amount 
of perco¬ 
late col¬ 
lected. 
Tree 
No. 
Ph of per¬ 
colate. 
1920: 
Cc. 
Nov. 2. 
Nutrient solution. 
TOO 
I 
6.8 
Do. 
.do. 
100 
2 
6. 7 
Nov. 29. 
Distilled water. 
'^OO 
I 
7. 2? 
Do. 
.do. 
0 ^ 
500 
2 
/ D 
6. 6 
1921: 
Mar. 28. 
.do. 
^OO 
I 
5. 4 
Do. 
.do. 
KOO 
2 
6- 5 
Apr. 20. 
,, do. 
10 
I 
Do. 
.do. 
10 
2 
6. 7 
